To conduct the study, researchers with the University of North Georgia looked at six different ball pits used in children’s physical therapy facilities. There, the pits are used to “provide stimulation to children with sensory or motor impairments,” per a news release on the findings.

At each ball pit location, researchers collected nine to 15 balls from different depths. By the end, they found “considerable microbial colonization in ball pits that were tested, including eight bacteria and one yeast that could cause disease,” researchers said.

“Bacterial colonization was found to be as high as thousands of cells per ball, clearly demonstrating an increased potential for transmission of these organisms to patients and an increased possibility of infection,” they added.

In total, 31 different bacterial species and one yeast species were found in the ball pits. More specifically, researchers determined Enterococcus faecalis, Staphylococcus hominis, Streptococcus oralis and Acinetobacter lwofii were present — all of which are “human-associated” bacteria that can cause nasty infections.

For instance, Enterococcus faecalis can cause endocarditis, septicemia, urinary tract infection and meningitis, while Staphylococcus hominis is “a cause of bloodstream infections and reported as a cause of sepsis in a neonatal intensive care unit,” the researchers said.

Researchers also noted the physical therapy clinics studied “may go days or weeks between cleanings" of the ball pits — just the right amount of time for these disease-causing microorganisms to grow to levels that can make children ill.

"We found considerable variation in the number of microorganisms between the different ball pit samples," Mary Ellen Oesterle, the study’s lead author, said in a statement. "This suggests that clinics utilize different protocols for cleaning and maintenance, potentially representing a broader need to clarify and establish standards that reduce the risk of transmission."